Federal Health Minister Greg Hunt insists up to 100 lives a year can be saved when codeine is taken off store shelves this week.
From Thursday codeine-based pain medication will no longer be available over the counter at pharmacies and shops.
Customers will have to get a prescription from their doctor under the publicly criticised changes decided by the Therapeutic Goods Administration.
Mr Hunt says codeine is addictive and dangerous and Australia's over-the-counter ban will match others in the US and UK.
"We know that there are over half a million Australians with some form of codeine addiction," he told ABC radio on Tuesday.
"It would be almost unthinkable for any responsible government to ignore the unanimous advice of medical authorities."
The minister pointed to a greater availability of paracetamol and ibuprofen combination medications and talked up the nation's high bulk billing rates when quizzed about the frustration and cost of having to see a doctor for a script.
In October, all state health ministers - bar South Australia - wrote to Mr Hunt urging him to rework the codeine reforms.
NSW Health Minister Brad Hazzard has warned people may try and get codeine from emergency departments instead.
"The problem with this decision is that GPs might not be available when people are in pain, or they may charge $70 to $80 more (by way of consultation fees) for something people used to be able to get over the counter for less than $10," he told The Australian on Tuesday.
A prescription is required for codeine products in some other European countries including Austria, Belgium, Germany and Italy, as well as Japan and the United Arab Emirates.
MEDICINE REQUIRING A PERSCRIPTION FROM THURSDAY:
* Codeine-containing painkillers, such as Panadeine, Nurofen Plus and Mersyndol.
* Codeine-containing cold and flu products, such as Codral and Demazin.